1. Field of the Invention
This invention relates to a diagnostic apparatus of a metal processing machine such as, for example, a lathe and more particularly, to a diagnostic apparatus for a machine which is capable of setting a predetermined target value of variable to be controlled such as the position of or the speed needed for transferring position of a machine and/or its component members and executing automatic control operations to allow the variable to be controlled to correctly match the predetermined value.
2. Description of the Prior Art
Recently, the operations of a conventional metal processing machine such as a lathe are properly controlled by computer means. FIG. 1 is the schematic diagram showing an example of the constitution of a machine controlled by a computer.
The essential part of the computer-controlled machine 1 is provided with a pair of jaw members 11 and 12 used for holding the object to be processed. Driving mechanisms 21 and 22 cause these jaw members 11 and 12 to separate from and come closer to each other by moving the positions of the jaw members 11 and 12.
Motors as the driving sources 32 and 32 respectively drive the driving mechanisms 21 and 22, while these motors 31 and 32 are controlled by the control signals delivered from controlling means 5 described later on.
Position-sensors 41 and 42 respectively detect positions of the jaw members 11 and 12 of the machine 1 to be controlled. These sensors 41 and 42 are respectively secured to their bases for correctly sensing the relative positions of the jaw members 11 and 12. Data related to the detected positions of the jaw members 11 and 12 is delivered from sensors 41 and 42 to controller means 5 which applies control operations using fed-back control system.
As mentioned above, data related to the detected positions of the jaw members 11 and 12 is fed back to controlling means 5 from sensors 41 and 42. On receipt of the position data signal, controlling means 5 outputs control signals to motors 31 and 32.
The reference numeral 6 denotes setting means. This setting means may, for example, be part of the host control unit comprised of a microcomputer. An operator can either set the positions of those jaw members 11 and 12, or use the setting means 6. Generally, the detected position data is inputted to setting means 6 as the target value signal from the CPU which is not shown in FIG. 1. In other words, the data of specifying the interval 7 which should be set between the jaw members 11 and 12 are inputted to setting means 6 as the target value. Setting means 6 delivers data indicative of the target value to controlling means 5 as the aim-target value of the variable. Controlling means 5 then reads the respective positions of the jaw members 11 and 12, i.e., the variable, of the jaw members 11 and 12 detected by sensors 41 and 42 in order to ascertain the interval 7 between the jaw members 11 and 12, and the controlling means 5 determines a difference between the ascertained interval 7 and the target value delivered from setting means 6, and finally it outputs a specific control signal to motors 31 and 32 to make the difference zero. As a result, motors 31 and 32 are properly activated to allow controlling means 5 to execute feedback control operation to move the jaw members 11 and 12 so that the interval 7 between the jaw members 11 and 12 coincides with the target value inputted to setting means 6. The amount of the movement of the jaw members 11 and 12 corresponds to the displacement values of the variable.
Conventionally, in driving any machine having the typical constitution mentioned above, an operator has detected any failure or malfunction of machine itself or the driving and control systems in the manner shown below.
Normally, the operator judges the condition of the machine at the time of inspection before starting the operation, either by reference to the operating manual or on the basis of his own experiences. However, the operator can find failure of electrical control system only in the event of actual inoperativeness of the machine 1 itself, driving mechanisms 21 and 22 and motors 31 and 32. There is therefore a need to preliminarily detect any failure of machine itself and its component system and a need to always keep servicing staff for providing maintenance services.